I wonder if there is a "unified" source for map color conventions, that GIS map builders are encouraged to follow?

EDIT

To clear up my question a bit. I'm more interested in the color <-with respect to the -> object it represents. For example, when you look at a map, and see "blue", the assumption could be water; however, it gets a bit shady when talking about let's say property maps: "is it pink or grey for industrial?". It'll be nice if there were such conventions whether lose or rigid about associating color to map-object

below you clarify you are looking for colours and "their meanings", though here you say you are looking for conventions
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mdsumnerNov 24 '10 at 21:30

Because color meanings vary with culture and application (see a perceptive comment by @Sean below), we shouldn't expect one correct answer to this question: it ought to be CW.
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whuber♦Nov 27 '10 at 2:12

7 Answers
7

I think the literal answer to your question is "not really" (aside from things like blue=water or blue/red=Dem/Rep). It depends on how/what other data is displayed on a map and the map's purpose whether, for example, county boundaries are a light color or dark color.

If you are wondering about a specific type of data, like land use or zoning, it might be good to further narrow down your question. Also, I've always found it helpful to look at other maps and see how they've handled the same sort of data. I see some of the ESRI Map Books are online... http://www.esri.com/mapmuseum/index.html

Agreed. Color is symbology and you can't have a universal symbology that's useful in any meaningful way. Most conventions are going to be project or, at least, industry specific. On top of that you could have cultural differences to consider.
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SeanNov 23 '10 at 21:11

I say this because, when I was doing geography in high school, it was quite the taboo to draw anything other than water on the map as blue. Often losing marks when we did, even getting close to purple was avoided.

When I went to college, major highways were colored blue, in fact, a trademark blue; Nova Scotia Blue.
At the same time, the cartography teacher would mention that a good map doesn't have/need a legend.

When I make maps for First Nation communities, the Reserve/Community area is often preferred to be seen in shades of red. Working in government making the same maps, using red is considered derogatory. Cultural relevance plays a big part here, easy to offend person(s).

From my experience, such conventions are developed locally. Cross reference with maps produced in the same manner.

I recently came across some of the work of Sidonie Christophe that has particular bearing to this subject. While in the particular paper I'm referencing (Christophe, 2011) she proposes a more general set of cartographic rules governing the choice of color for objects, the rules she proposes are so intuitive that I suspect they are in general implemented in most cartographic concepts anyway. In essence, for particular objects she suggests mapping colors to the respective intuit color representation we hold for those objects (semiotics). One of the most obvious examples of this was already given in several of the answers to this thread (blue for water by neuhausr).

But, the novelty in her work is not the actual set of rules she proposes, but the acknowledgement that the actual choice set of colors we often use are arbitrary. Particular objects often have no intrinsic color mapping, but they still need to be represented and contrasted to a degree by color to be able to be distinguish those particular objects on a map. She notes that because it is arbitrary, we should choose these color mappings based on what is aesthetically pleasing, and she gives examples of using famous pieces of artwork to choose the contrasting color palette. While she admits that the choice of a particular set of colors can not be determined optimal in any objective sense, we can use popular pieces of artwork to help guide our choice of color contrast.

Below I have posted an example of her work using a color palette from a Vincent Van Gogh painting for choosing a set of different color mappings for objects (from page 159 of her dissertation)

If you can get a copy of her recent article in The Cartographic Journal I would suggest it (as this is only a minor distillation of the rules she proposes), or alternatively if you can read French in appears most of the same information is contained in her dissertation. I think her suggestions are really applicable/useful in instances in which we need to represent many objects on the map and the objects are highly disjoint in their nature (e.g. land use variables) and have no intrinsic color mapping. It also results in a very palatable maps even when there are many objects that need to be contrasted.

RGB
For Screen output (Like Web, TV or PDF) - Use RGB (Red, Green, Blue)
Black is more a mixture of all and is more a muddy brown.

Comparisons between RGB displays and CMYK prints can be difficult, since the color reproduction technologies and properties are so different. A computer monitor mixes shades of red, green, and blue to create color pictures. A CMYK printer instead uses light-absorbing cyan, magenta and yellow inks, whose colors are mixed using dithering, halftoning, or some other optical technique.

Pantone

http://en.wikipedia.org/wiki/Pantone
can also confuse the issue with RGB/CMYK
Pantone (specific to Printing - Pantone system also allows for many 'special' colours to be produced such as metallic's and fluorescent's)

Tend to work at CMYK then convert to RGB

BLUE (RGB is blue but CMYK cyan in ink)

CMYK 'K' =KEY for Key Plate represents Black not to be confused with Blue.

Nice details, but your question answers, "What are some available color spaces?", not "What common colors are used for certain objects in GIS?".
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Michael ToddNov 17 '10 at 20:22

Colour is determined on the subject matter and the media output. Red on the map usually means 'danger' but on a Web page/TV screen animation symbol colour can be multiple red/yellow to indicate danger.
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Mapperz♦Nov 17 '10 at 21:01